Agglomeration control using early transition metal alloys

ABSTRACT

Structures and methods of fabricating portions of integrated circuit devices to reduce agglomeration tendencies of high surface-energy metals used in interconnects and contacts. Early transition metals having relatively low surface energies are chosen to form stable crystalline compounds rich in the high surface-energy metal. Agglomeration control layers containing such alloy compounds facilitate adhesion between the high surface-energy metal and an underlying layer of the integrated circuit device, such as a diffusion barrier layer. These agglomeration control layers may be nitrided to improve robustness at higher temperatures.

CROSS-REFERENCE TO RELATED APPLICATION

This is a divisional application of U.S. patent application Ser. No. 09/896,093, titled AGGOLMERATION CONTROL USING EARLY TRANSISITION METAL ALLOYS, filed Jun. 28, 2001 (pending), which application is assigned to the assignee of the present invention and the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to fabrication of integrated circuit devices, and in particular to the use of early transition metal alloys and their nitrides to reduce the agglomeration tendencies of metals used to form interconnects and other conductors within an integrated circuit device.

BACKGROUND OF THE INVENTION

In the fabrication of a semiconductor integrated circuit device, it is desirable to fabricate the device with materials having a low resistivity (i.e., property of resistance to current flow) in order to optimize the device's electrical performance. Lower resistance within the device allows faster processing of information due to a smaller delay time associated with resistance to current flow.

Various portions of an integrated circuit device are typically interconnected using metal lines (i.e., conductive layers) with metal contacts extending to active areas within the device. Resistivity of the metal lines plays an increasingly important role in the overall resistance of an integrated circuit device. As such devices become more dense, wiring length increases. Furthermore, wiring pitch decreases, which effectively decreases the available wiring width. As the wiring width decreases, resistivity of the wiring material becomes a dominant factor as compared to parasitic capacitance between wires (i.e., that associated with device resistance). Thus, it is desirable to decrease the resistivity of wiring material within an integrated circuit device.

Copper (Cu) and silver (Ag) are becoming increasingly desirable in integrated circuit fabrication as a replacement for aluminum (Al), particularly for interconnect lines and other conductive structures (i.e., conductive digit lines and plugs connecting the conductive layers). Copper and silver have lower resistivity and higher resistance to electromigration (i.e., the transport of metal atoms in conductors carrying large current densities, resulting in morphological degradation of the conductors) than aluminum.

These metal interconnects and contacts are typically formed using a dual damascene technique. In a dual damascene process, a dielectric layer is formed over a semiconductor substrate in which the integrated circuit device is being fabricated. Vias are formed in the dielectric layer to expose active areas of the semiconductor substrate and trenches are formed in the dielectric layer to couple the vias to other portions of the integrated circuit device. A metal layer is then blanket deposited to fill the trenches and vias and to cover the dielectric layer. The excess metal overlying the dielectric layer is removed, such as by chemical-mechanical planarization (CMP) to define the metal interconnects as the metal-filled trenches and metal contacts as the metal-filled vias. A CMP process generally involves abrading the surface of the semiconductor substrate with an abrasive and a solution to chemically assist the abrasive. The abrasive/solution combination is generally specific to the material to be removed and to the surrounding materials to be retained.

To reduce migration or diffusion of copper or silver into the underlying substrate, a diffusion barrier layer is often interposed between the substrate and the metal layer. Tantalum nitride is one material used as a diffusion barrier layer between the substrate and the metal layer. Continuous copper and silver layers are readily formed over tantalum nitride. However, it is generally necessary to use two different abrasive/solution combinations to first remove the copper or silver layer and then remove the tantalum nitride layer. While the use of titanium nitride as a diffusion barrier layer facilitates the use of a single abrasive/solution combination, it can be difficult to form copper or silver layers on a titanium nitride layer. Because of their large surface energies, copper and silver tend to agglomerate on a titanium nitride layer, thus tending to result in a discontinuous film and the production of voids in the damascene structure.

For the reasons stated above, and for other reasons stated below that will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for alternative structures and methods for utilizing copper, silver and other high surface-energy metals as integrated circuit interconnect materials.

SUMMARY

Structures and methods of fabricating portions of integrated circuit devices are described to reduce agglomeration tendencies of high surface-energy metals used in interconnects and contacts. Early transition metals having relatively low surface energies are chosen to form stable crystalline compounds rich in the high surface-energy metal. Agglomeration control layers containing such alloy compounds facilitate adhesion between the high surface-energy metal and an underlying layer of the integrated circuit device, such as a diffusion barrier layer. These agglomeration control layers may be nitrided to improve robustness at higher temperatures.

For one embodiment, the invention provides a portion of an integrated circuit device. The portion includes a diffusion barrier layer and a first metal layer on the diffusion barrier layer. The first metal layer contains a crystalline alloy compound containing a first metal component and a second metal component, wherein the second metal component is selected from the group consisting of Group IIIA and Group IVA elements. An atomic ratio of the first metal component to the second metal component in the first metal layer is greater than one. The portion further includes a second metal layer on the first metal layer, wherein the second metal layer contains the first metal component. The diffusion barrier layer may be a titanium-containing material such as titanium nitride.

For another embodiment, the invention provides a portion of an integrated circuit device. The portion includes a diffusion barrier layer and a nitrided metal layer on the diffusion barrier layer. The nitrided metal layer contains a first metal component, a second metal component and nitrogen. The second metal component is selected from the group consisting of Group IIIA and Group IVA elements. An atomic ratio of the first metal component to the second metal component in the nitrided metal layer is greater than one. The portion further includes a second metal layer on the first metal layer, wherein the second metal layer contains the first metal component. The diffusion barrier layer may be a titanium-containing material such as titanium nitride.

For yet another embodiment, the invention provides a portion of an integrated circuit device. The portion includes a titanium nitride layer and a nitrided metal layer on the titanium nitride layer. The nitrided metal layer contains copper, a metal component capable of forming a crystalline compound with the copper, and nitrogen. The metal component is selected from the group consisting of scandium, yttrium, lanthanum, titanium, zirconium and hafnium. An atomic ratio of copper to the metal component in the nitrided metal layer is greater than one. The portion further includes a layer of metal on the nitrided metal layer, wherein the layer of metal contains copper.

For still another embodiment, the invention provides a portion of an integrated circuit device. The portion includes a titanium nitride layer and a nitrided metal layer on the titanium nitride layer. The nitrided metal layer contains silver, a metal component capable of forming a crystalline compound with the silver, and nitrogen. The metal component is selected from the group consisting of scandium, yttrium and lanthanum. An atomic ratio of silver to the metal component in the nitrided metal layer is greater than one. The portion further includes a layer of metal on the nitrided metal layer, wherein the layer of metal contains silver.

Further embodiments of the invention include apparatus of varying scope.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A–1F are cross-sectional views of a portion of an integrated circuit device at various stages of fabrication in accordance with one embodiment of the invention.

FIG. 2 is a binary phase diagram for a copper-scandium binary system.

DETAILED DESCRIPTION

In the following detailed description of the present embodiments, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that process, electrical or mechanical changes may be made without departing from the scope of the present invention. The terms wafer or substrate used in the following description include any base semiconductor structure. Examples include silicon-on-sapphire (SOS) technology, silicon-on-insulator (SOI) technology, thin film transistor (TFT) technology, doped and undoped semiconductors, epitaxial layers of a silicon supported by a base semiconductor structure, as well as other semiconductor structures well known to one skilled in the art. Furthermore, when reference is made to a wafer or substrate in the following description, previous process steps may have been utilized to form regions/junctions in the base semiconductor structure, and the terms wafer and substrate include the underlying layers containing such regions/junctions. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims and equivalents thereof.

FIGS. 1A–1F are cross-sectional views of a portion of an integrated circuit device 100 at various stages of fabrication. In FIG. 1A, a dielectric layer 110 is formed on a base layer 105. For one embodiment, the base layer 105 is a semiconductor substrate, such as a monocrystalline silicon substrate. Other semiconductor substrates are known and used in the art of semiconductor fabrication. For additional embodiments, the base layer 105 may be conductor layer. For example, the base layer 105 may be a metal line or other conductive interconnect, such as a Metal 1 layer, Metal 2 layer, Metal 3 layer, etc.

Dielectric layer 110 contains an insulator or dielectric material, such as a silicon oxide (SiO/SiO₂), silicon nitride (SiN/Si₂N/Si₃N₄) or silicon oxynitride (SiO_(x)N_(y)) material. For one embodiment, the dielectric layer 110 contains a doped silicon oxide material, such as borophosphosilicate glass (BPSG), a boron- and phosphorous-doped silicon dioxide material. Other dielectric materials are known and used in the art of semiconductor fabrication.

The dielectric layer 110 is patterned to define recesses or apertures such as trenches 112 and vias 114 as depicted in FIG. 1A. Patterning of the dielectric layer 110 may include conventional photolithographic techniques to mask portions of the dielectric layer 110 and to expose portions of the dielectric layer 110 where future trenches 112 and vias 114 are to be formed. The exposed portions of the dielectric layer 110 are then removed. The portions of the dielectric layer 110 may be removed by etching or other suitable removal technique known in the art. Removal techniques are generally dependent upon the material of construction of the layer to be removed as well as the surrounding or underlying layers to be retained.

Due to the nature of the dual damascene process, the depth of the etch is variable across the surface of the device 100, e.g., the etch depth is greater where vias 114 are defined and less where only trenches 112 are defined. Thus, two mask and etch steps can be utilized in a conventional photolithographic process to define the vias 114 separately from the trenches 112. Alternatively, a gray mask pattern can be utilized to define the vias 114 and trenches 112 simultaneously in one photolithographic mask and etch step. The trenches 112 will form interconnect lines for the integrated circuit device while the vias 114 will form contacts to active areas of the integrated circuit.

Following patterning of the dielectric layer 110, a diffusion barrier layer 115 is formed overlying the dielectric layer 110 and the exposed portions of the base layer 105 in FIG. 1B. The diffusion barrier layer 115 preferably covers the sidewalls and bottoms of the trenches 112 and vias 114 as well as the surface of the dielectric layer 110. Portions of the diffusion barrier layer 115 covering bottoms of the vias 114 are in contact with the underlying base layer 105, which may be an active area of a semiconductor substrate of the integrated circuit device 100 or an underlying interconnect of the integrated circuit device 100. For one embodiment, the diffusion barrier layer 115 is a titanium-containing layer. For a further embodiment, the diffusion barrier layer 115 is a titanium nitride layer.

An agglomeration control layer 120 is formed on the diffusion barrier layer 115 as a metal layer or a nitrided metal layer. For one embodiment, the agglomeration control layer 120 contains an early transition metal alloy of the form MT_(x), where M is a first metal component, T is a Group IIIA or Group IVA transition metal and x is the atomic fraction of T. These early transition metal alloys contain a first metal component, M, that will be found in a subsequently-formed metal layer. For example, where copper (Cu) will be used as the major component of the interconnect structure, the first metal component of the agglomeration control layer 120 is chosen to be copper. Additional examples for the first metal component include noble and near noble metals such as silver (Ag), gold (Au), palladium (Pd), platinum (Pt), rhenium (Rh), iridium (Ir), ruthenium (Ru) and osmium (Os). Preferred metals for the interconnects and contacts typically have a high surface energy, which leads to difficulties in forming continuous layers due to a tendency to agglomerate during or after deposition.

The early transition metal alloys further contain a second metal component having a low surface energy relative to the metals used for the interconnects and contacts. The second metal component is a Group IIIA or Group IVA element as designated by the traditional IUPAC version of the periodic table. Such Group IIIA elements include scandium (Sc), yttrium (Y) and lanthanum (La). Such Group IVA elements include titanium (Ti), zirconium (Zr) and hafnium (Hf). Note that other versions of the periodic table are known using different designations for these same groups. The second metal component is capable of forming stable crystalline compounds with the first metal component. The early transition metals of Group IIIA and Group IVA have low surface energies, thus permitting improved adhesion to the underlying diffusion barrier layer 115.

The agglomeration control layer 120 is rich in the first metal component, i.e., the atomic ratio of the first metal component to the second metal component is greater than one. For better adhesion to the subsequent metal layer, the atomic ratio of the first metal component to the second metal component in the agglomeration control layer 120 is preferably greater than two.

For one class of embodiments using copper for the interconnects and contacts, the early transition metal alloys are copper-rich alloys containing copper and at least one Group IIIA or Group IVA element capable of forming a stable crystalline compound with copper. Such stable crystalline compounds can be readily determined from binary alloy phase diagrams of the two compounds of interest. For example, FIG. 2 is a binary phase diagram for the copper-scandium binary system as reported in Binary Alloy Phase Diagrams: Second Edition, Massalski, T. B., editor, The Materials Information Society, 1990. From FIG. 2, it can be seen that stable crystalline structures or equilibrium phases are found as Cu, CU₄SC, Cu₂Sc, CuSc, αSc and βSc. From these stable crystalline structures, Cu₄Sc and Cu₂Sc are copper-rich alloys and thus suitable for use with various embodiments. For alloys of other binary systems, appropriate binary alloy phase diagrams can be obtained or generated in order to identify stable crystalline structures.

For one embodiment, the agglomeration control layer 120 is a copper-rich alloy containing Cu₄Sc. For another embodiment, the agglomeration control layer 120 is a copper-rich alloy containing Cu₆Y. For yet another embodiment, the agglomeration control layer 120 is a copper-rich alloy containing Cu₄Ti. For still another embodiment, the agglomeration control layer 120 is a copper-rich alloy containing Cu₃Ti. For a further embodiment, the agglomeration control layer 120 is a copper-rich alloy containing Cu₅Zr.

For another class of embodiments using silver for the interconnects and contacts, the early transition metal alloys are silver-rich alloys containing silver and at least one Group IIIA element capable of forming a stable crystalline compound with silver. For one embodiment, the agglomeration control layer 120 is a silver-rich alloy containing Ag₄Sc. For another embodiment, the agglomeration control layer 120 is a silver-rich alloy containing Ag₄Y.

The crystalline alloy portions of the agglomeration control layer 120 generally provide reduced surface energies relative to amorphous films of the same metal components. This leads to improved adhesion between the agglomeration control layer 120 and the underlying diffusion barrier layer 115. Because crystalline alloy structures are more stable than amorphous alloys, crystalline alloys are also easier to fabricate with high levels of repeatability relative to amorphous alloys of the same metal components. Ease of fabrication and repeatability are important factors in reducing the cost of the integrated circuit device and in increasing its reliability.

Another consideration in the fabrication of the agglomeration control layer 120 is its electrical resistance. In general, higher levels of the first metal component will lead to lower resistance levels of the agglomeration control layer 120 and improved device performance. While crystalline alloy portions of the agglomeration control layer 120 provide improved adhesion to the underlying diffusion barrier layer 115, it is not necessary that the agglomeration control layer consist solely of crystalline structures of the first and second metal components. Regions of crystalline alloy structures can serve as nuclei for the growth of regions containing the first metal component in a substantially pure or elemental state. These regions of crystalline alloy structures provide the desired adhesion between the first metal component and the diffusion barrier layer 115. Thus, for additional embodiments, the agglomeration control layer 120 contains an amount of the first metal component in its elemental state. For one embodiment, at least 25 wt % of the agglomeration control layer 120 is the first metal component in its elemental state. For another embodiment, at least 50 wt % of the agglomeration control layer 120 is the first metal component in its elemental state. For a further embodiment, the atomic ratio of the first metal component to the second metal component is greater than 10. For a still further embodiment, the atomic ratio of the first metal component to the second metal component is greater than 20.

The agglomeration control layer 120 is preferably formed by physical vapor deposition (PVD) techniques. Examples include thermal evaporation, electron-beam evaporation and sputtering techniques well known in the art. PVD techniques are preferred as the crystalline structure is easily maintained during formation of the agglomeration control layer. A target, ingot or other source containing the crystalline alloy compound can be molded, pressed or otherwise formed for use in the chosen PVD technique.

For embodiments having an atomic ratio of the first metal component to the second metal component higher than the atomic ratio in the crystalline alloy compound, the PVD source may be a composite source containing a first portion of the crystalline alloy compound and a second portion of a material having increased levels of the first metal component, preferably other stable crystalline structures of the binary system and more preferably the first metal component in its elemental state. The first and second portions of the composite source are preferably intermixed to more easily form an agglomeration control layer 120 having a uniform composition. For example, a PVD source could be pressed from powdered Cu₄Sc and pure copper to produce a composite source having an atomic ratio of copper to scandium of greater than four to one.

The composite source may further contain more than two metal components. For example, the composite source may contain a first metal component in its elemental state, a first crystalline alloy compound of the first metal component and a Group IIIA or Group IVA element, and a second crystalline alloy compound of the first metal component and a different Group IIIA or Group IVA element. PVD sources may further contain additional components that do not materially affect the basic and novel properties of the agglomeration control layers disclosed herein.

For one embodiment, the agglomeration control layer 120 contains an early transition metal alloy nitride. Metal alloy nitrides containing the first and second metal components are generally more robust at higher temperatures than their corresponding metal alloy. To produce a metal alloy nitride, the PVD process can be carried out in an atmosphere containing nitrogen (N₂). For example, the agglomeration control layer 120 can be formed by a reactive sputtering process using a target containing a crystalline alloy compound rich in the first metal component. During the reactive sputtering process, a nitrogen-containing atmosphere is created in the deposition chamber. The nitrogen-containing atmosphere preferably contains nitrogen and a noble or inert gas, e.g., argon (Ar). The nitrogen reacts with the first and second metal components in the target during deposition to form a metal alloy nitride of the form MT_(x)N_(y), where M is the first metal component, T is a Group IIIA or Group IVA transition metal of the second metal component, N is nitrogen, x is the atomic fraction of T and y is the atomic fraction of N. For a further embodiment, the nitrogen-containing atmosphere contains approximately 5% to 30% nitrogen by volume.

Following formation of the agglomeration control layer 120, a metal layer 130 is formed. The metal layer 130 is generally formed as a blanket deposition in dual damascene techniques. This fills the trenches 112 and vias 114 by covering the entire surface of the dielectric layer 110 with the metal layer 130. The metal layer 130 may be formed using chemical vapor deposition (CVD) or physical vapor deposition (PVD) techniques. Additionally, the metal layer 130 may be formed using electroplating techniques, which may include first forming an optional seed layer 125 overlying the agglomeration control layer 120, as shown in FIG. 1D, followed by electroplating the remaining portion of the metal layer 130 onto the seed layer 125 resulting in the structure shown in FIG. 1E. The seed layer 125 contains the first metal component. For one embodiment, the seed layer 125 consists essentially of the first metal component.

Electroless plating is another example of a process that may be used to form the metal layer 130 covering the surface of the integrated circuit device 100. The metal layer 130 contains the first metal component of the agglomeration control layer 120. For example, where the first metal component of the agglomeration control layer 120 contains copper, silver, gold, palladium, platinum, rhenium, iridium, ruthenium or osmium, the metal layer 130 contains copper, silver, gold, palladium, platinum, rhenium, iridium, ruthenium or osmium, respectively. The metal layer 130 is preferably not a composite material. For one embodiment, the metal layer 130 consists essentially of the first metal component.

As the dual damascene approach uses a contiguous metal layer 130 to fill the trenches 112 and vias 114, excess portions of the metal layer 130 must generally be removed from the surface of the dielectric layer 110. Removal of the excess portions of the metal layer 130, along with excess portions of the agglomeration control layer 120 and the diffusion barrier layer 115, generally involves some mechanical action, such as chemical-mechanical planarization (CMP). CMP is sometimes also referred to as chemical-mechanical polishing. Removal of the excess portions of the metal layer 130 defines interconnect lines 132 and contacts 134 as shown in FIG. 1F.

The foregoing figures were used to aid the understanding of the accompanying text. However, the figures are not drawn to scale and relative sizing of individual features and layers are not necessarily indicative of the relative dimensions of such individual features or layers in application. Accordingly, the drawings are not to be used for dimensional characterization.

CONCLUSION

Structures and methods of fabricating portions of integrated circuit devices have been described to reduce agglomeration tendencies of high surface-energy metals used in interconnects and contacts. Early transition metals having relatively low surface energies are chosen to form stable crystalline compounds rich in the high surface-energy metal. Agglomeration control layers containing such alloy compounds facilitate adhesion between the high surface-energy metal and an underlying layer of the integrated circuit device, such as a diffusion barrier layer. These agglomeration control layers may be nitrided to improve robustness at higher temperatures.

Copper-rich or silver-rich agglomeration control layers described herein are especially beneficial in copper or silver damascene structures, respectively, as they facilitate the use of a titanium nitride diffusion barrier layer. Use of a titanium nitride diffusion barrier layer in copper or silver damascene structures permits use of a single slurry in a chemical-mechanical planarization process to remove the excess copper or silver as well as the excess diffusion barrier layer.

Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement that is calculated to achieve the same purpose may be substituted for the specific embodiments shown. Many adaptations of the invention will be apparent to those of ordinary skill in the art. Accordingly, this application is intended to cover any adaptations or variations of the invention. It is manifestly intended that this invention be limited only by the following claims and equivalents thereof. 

1. An interconnect of an integrated circuit device, comprising: a diffusion barrier layer; a first metal layer on the diffusion barrier layer, wherein the first metal layer comprises a first metal component and a second metal component forming a crystalline compound with the first metal component, wherein the second metal component has a surface energy lower than a surface energy of the first metal component, and wherein the crystalline compound is rich in the first metal component; and a second metal layer on the first metal layer, wherein the second metal layer comprises the first metal component; wherein the first metal component is selected from the group consisting of silver, gold, palladium, platinum, rhenium, iridium, ruthenium and osmium.
 2. The interconnect of claim 1, wherein the diffusion barrier layer is a titanium-containing layer.
 3. The interconnect of claim 1, wherein the diffusion barrier layer is titanium nitride.
 4. The interconnect of claim 1, wherein the second metal component is selected from the group consisting of scandium, yttrium, lanthanum, titanium, zirconium and hafnium.
 5. The interconnect of claim 1, wherein the first metal layer further comprises a third metal component forming a second crystalline compound with the first metal component, wherein the third metal component is different from the second metal component, wherein the third metal component has a surface energy lower than a surface energy of the first metal component, and wherein the second crystalline compound is rich in the first metal component.
 6. A portion of an integrated circuit device, comprising: a dielectric layer overlying a base layer; a layer of titanium nitride overlying the dielectric layer; a first metal layer on the layer of titanium nitride, wherein the first metal layer comprises a crystalline alloy compound containing a first metal component and a second metal component, wherein the first metal component is selected from the group consisting of silver, gold, palladium, platinum, rhenium, iridium, ruthenium and osmium, wherein the second metal component is selected from the group consisting of Group IIIA and Group IVA elements, and wherein an atomic ratio of the first metal component to the second metal component in the first metal layer is greater than one; and a second metal layer on the first metal layer, wherein the second metal layer comprises the first metal component.
 7. The portion of an integrated circuit device of claim 6, wherein the atomic ratio of the first metal component to the second metal component in the first metal layer is greater than two.
 8. The portion of an integrated circuit device of claim 6, wherein the atomic ratio of the first metal component to the second metal component in the first metal layer is greater than ten.
 9. The portion of an integrated circuit device of claim 6, wherein the atomic ratio of the first metal component to the second metal component in the first metal layer is greater than twenty.
 10. The portion of an integrated circuit device of claim 6, wherein the layer of titanium nitride is adjoining a portion of the dielectric layer.
 11. The portion of an integrated circuit device of claim 10, wherein the layer of titanium nitride is further adjoining a portion of the base layer.
 12. The portion of an integrated circuit device of claim 6, wherein the base layer is selected from the group consisting of a semiconductor substrate and a conductor layer.
 13. An interconnect of an integrated circuit device, comprising: a titanium nitride layer; a first metal layer on the titanium nitride layer, wherein the first metal layer comprises copper and a metal component forming a crystalline compound with the copper, wherein the metal component is selected from the group consisting of scandium and yttrium, and wherein the crystalline compound has an atomic ratio of copper to the metal component in the first metal layer of greater than one; and a second metal layer on the first metal layer, wherein the second metal layer comprises copper.
 14. A portion of an integrated circuit device, comprising: a layer of titanium nitride adjoining a dielectric layer; a metal layer on the layer of titanium nitride, wherein the metal layer comprises a copper-rich alloy selected from the group consisting of Cu₄Sc, Cu₆Y, Cu₄Ti, Cu₃Ti and Cu₅Zr; and a copper layer on the metal layer.
 15. The portion of an integrated circuit device of claim 14, wherein the copper-rich alloy has a crystalline structure.
 16. The portion of an integrated circuit device of claim 14, wherein the metal layer further comprises elemental copper.
 17. The portion of an integrated circuit device of claim 16, wherein at least 25 wt % of the metal layer is the elemental copper.
 18. The portion of an integrated circuit device of claim 16, wherein at least 50 wt % of the metal layer is the elemental copper.
 19. The portion of an integrated circuit device of claim 14, wherein the layer of titanium nitride is further adjoining a base layer selected from the group consisting of a semiconductor substrate and a conductor layer.
 20. An interconnect of an integrated circuit device, comprising: a layer of titanium nitride; a first metal layer on the layer of titanium nitride, wherein the first metal layer comprises elemental copper, wherein the first metal layer further comprises a copper-rich crystalline alloy compound containing copper and a metal component selected from the group consisting of scandium and yttrium, and wherein at least 25 wt % of the first metal layer is elemental copper; and a second metal layer on the first metal layer, wherein the second metal layer comprises copper.
 21. An interconnect of an integrated circuit device, comprising: a layer of titanium nitride; a first metal layer on the layer of titanium nitride, wherein the first metal layer comprises elemental copper, wherein the first metal layer further comprises a copper-rich crystalline alloy compound containing copper and a metal component selected from the group consisting of scandium and yttrium, and wherein an atomic ratio of copper to the metal component in the first metal layer is greater than ten; and a second metal layer on the first metal layer, wherein the second metal layer comprises copper.
 22. An interconnect of an integrated circuit device, comprising: a titanium nitride layer; a first metal layer on the titanium nitride layer, wherein the first metal layer comprises silver and a metal component forming a crystalline compound with the silver, wherein the metal component is selected from the group consisting of scandium, yttrium and lanthanum, and wherein the crystalline compound has an atomic ratio of silver to the metal component in the first metal layer of greater than one; and a second metal layer on the first metal layer, wherein the second metal layer comprises silver.
 23. A portion of an integrated circuit device, comprising: a layer of titanium nitride adjoining a dielectric layer; a metal layer on the layer of titanium nitride, wherein the metal layer comprises a silver-rich alloy selected from the group consisting of Ag₄Sc and Ag₄Y; and a silver layer on the metal layer.
 24. The portion of an integrated circuit device of claim 23, wherein the silver-rich alloy has a crystalline structure.
 25. The portion of an integrated circuit device of claim 23, wherein the metal layer further comprises elemental silver.
 26. The portion of an integrated circuit device of claim 25, wherein at least 25 wt % of the metal layer is the elemental silver.
 27. The portion of an integrated circuit device of claim 25, wherein at least 50 wt % of the metal layer is the elemental silver.
 28. The portion of an integrated circuit device of claim 23, wherein the layer of titanium nitride is further adjoining a base layer selected from the group consisting of a semiconductor substrate and a conductor layer.
 29. An interconnect of an integrated circuit device, comprising: a layer of titanium nitride; a first metal layer on the layer of titanium nitride, wherein the first metal layer comprises elemental silver, wherein the first metal layer further comprises a silver-rich crystalline alloy compound containing silver and a metal component selected from the group consisting of scandium, yttrium and lanthanum, and wherein at least 25 wt % of the first metal layer is elemental silver; and a second metal layer on the first metal layer, wherein the second metal layer comprises silver.
 30. An interconnect of an integrated circuit device, comprising: a layer of titanium nitride; a first metal layer on the layer of titanium nitride, wherein the first metal layer comprises elemental silver, wherein the first metal layer further comprises a silver-rich crystalline alloy compound containing silver and a metal component selected from the group consisting of scandium, yttrium and lanthanum, and wherein an atomic ratio of silver to the metal component in the first metal layer is greater than ten; and a second metal layer on the first metal layer, wherein the second metal layer comprises silver.
 31. A portion of an integrated circuit device, comprising: a dielectric layer on a base layer; a titanium nitride layer overlying the dielectric layer; a nitrided metal layer on the titanium nitride layer, wherein the nitrided metal layer comprises silver, a metal component capable of forming a crystalline compound with the silver, and nitrogen, wherein the metal component is selected from the group consisting of scandium, yttrium and lanthanum, and wherein an atomic ratio of silver to the metal component in the nitrided metal layer is greater than one; and a silver layer on the nitrided metal layer.
 32. The portion of an integrated circuit device of claim 31, wherein a portion of the titanium nitride layer is adjoining a portion of the base layer.
 33. A portion of an integrated circuit device, comprising: a titanium nitride layer; a nitrided metal layer on the titanium nitride layer, wherein the nitrided metal layer comprises silver, a metal component capable of forming a crystalline compound with the silver, and nitrogen, wherein the metal component is selected from the group consisting of scandium, yttrium and lanthanum, and wherein an atomic ratio of silver to the metal component in the nitrided metal layer is greater than one; and a silver layer on the nitrided metal layer.
 34. A portion of an integrated circuit device, comprising: a layer of titanium nitride; a nitrided metal layer on the layer of titanium nitride, wherein the nitrided metal layer is of the form AgT_(x)N_(y), where Ag is silver, T is a Group IIIA transition metal, N is nitrogen, x is an atomic fraction of T, y is an atomic fraction of N, and x and y are each less than one; and a metal layer on the nitrided metal layer, wherein the metal layer comprises silver.
 35. The portion of an integrated circuit device of claim 34, wherein T is selected from the group consisting of scandium, yttrium and lanthanum.
 36. A portion of an integrated circuit device, comprising: a layer of titanium nitride; a nitrided metal layer on the layer of titanium nitride, wherein the nitrided metal layer is of the form AgT_(x)N_(y), where is silver, T is a Group IIIA transition metal, N is nitrogen, x is an atomic fraction of T, y is an atomic fraction of N, x is less than approximately 0.1 and y is less than approximately 0.9; and a silver layer on the nitrided metal layer. 